import { DiffPatcher } from 'jsondiffpatch/src/diffpatcher';

const defaultObjectHash = (o, idx) =>
  o === null && '$$null' ||
  o && (o.id || o.id === 0) && `$$id:${JSON.stringify(o.id)}` ||
  o && (o._id ||o._id === 0) && `$$_id:${JSON.stringify(o._id)}` ||
  '$$index:' + idx;

const defaultPropertyFilter = (name, context) =>
  typeof context.left[name] !== 'function' &&
  typeof context.right[name] !== 'function';

const defaultDiffPatcher = new DiffPatcher({
  arrays: { detectMove: false },
  objectHash: defaultObjectHash,
  propertyFilter: defaultPropertyFilter
});

export default function createDiffPatcher(objectHash, propertyFilter) {
  if (!objectHash && !propertyFilter) {
    return defaultDiffPatcher;
  }

  return new DiffPatcher({
    arrays: { detectMove: false },
    objectHash: objectHash || defaultObjectHash,
    propertyFilter: propertyFilter || defaultPropertyFilter
  });
}